Effect of Oxidation on Base Liquids of Oil and Synthetic-Based Drilling Fluids at High Pressures and High Temperatures
Bibliographic record
Abstract
Abstract Diesels and distillates are used as the base liquid for the majority of oil-based drilling fluids in conventional drilling and as the liquid phase in gasified liquids in some underbalanced drilling operations. They are also used as the friction reducing agents in situations such as freeing stuck pipe. Understanding the true downhole rheological properties is crucial as they affect equivalent circulating density, hole cleaning, barite sag, surge/swab pressures during tripping, pump pressure and bit hydraulics. Moreover, gelation and excessively high viscosity are major concerns, especially at high temperatures. This paper presents the results of an experimental investigation which was aimed at establishing the effect of oxidation on some base liquids for oil-based and synthetic based drilling fluids at high pressures and high temperatures. Base liquids were aged at 150 °C and 14 MPa initial pressure in the presence of air for 60 hours. Characterization of gas and liquid phases and measurements of solid phase has beencarried out. Viscosity measurements at temperatures and pressures ranging from 20 to 152 °C and atmospheric to 103.4MPa, respectively, have been performed. The viscosity of the liquid samples after aging is compared with that of corresponding fresh samples. The results show that the degree of oxidation plays an important role in increasing the sample viscosity. This increase in viscosity is a function of temperature, and is more significant at low temperatures. Furthermore, agitation of samples during aging with air resulted in increased amounts of solid precipitation while lowering the viscosity of the liquid phase. Introduction Historically, in-situ combustion (1),(2) and high pressure air injection (HPAI) (3) are two major areas in thermal enhanced oil recovery techniques that oxidation of oils are of special importance. In these processes it is of vital importance to know what effects the oxidation has on rheological properties of the oil, because it affects the mobility of the oil and therefore the recovery factor. Another area that in which oxidation of oils can be an issue is drilling a well. (4) Generally a well can be drilled either by conventional drilling or underbalanced drilling (UBD) techniques. (5) In conventional drilling employing oil-based drilling fluids in hot wells, the hot oil is returned to the surfacetanks and is exposed to air. Since the base liquids in oil-based drilling fluids are expensive, they are used in many wells before disposal. Therefore, even if the rate of oxidation is low, the long time of exposure can result in substantial oxidation of the oil.On the other hand, in underbalanced drilling a variety of different drilling fluids such as dry air, nitrogen, natural gas, mist, stable foam, stiff foam, gasified liquids (aerated muds), glass bubbles and liquids are used. (5) In some gasified liquids (aerated muds), the liquid phase is primarily light oils (diesels, distillates,...). Deoxygenated air from membrane units (air with about 5 percent oxygen content) is used as the gas phase. (6) In this case, oxidation is more severe, because deoxygenated air is continuously exposed to oil downhole at higher temperature and pressure conditions.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".